Various type chemical processes are commonly carried out in large, stirred vessels which are frequently provided with auxiliary equipment, such as baffles, agitator equipment, heat transfer coils which enable heat to be supplied or extracted from the contents of the vessels, and the like. In many cases, however, such processes eventually produce undesirable deposits on the surfaces of the equipment with which the reaction mixtures come into contact. Such deposits interfere with the efficient transfer of heat to and from the interior of the vessels. Further, these deposits have a tendency to deteriorate and partially fragment resulting in contamination of the reaction mixture and the products produced therefrom. This problem is particularly prevalent in polymerization-type reactions, since the deposits, or buildup, of solid polymer on reactor surfaces not only interferes with heat transfer, but decreases productivity and adversely affects polymer quality.
The polymer buildup problem is particularly troublesome in the commercial production of polymers and copolymers of vinyl and vinylidene halides, when polymerized alone or with other vinylidene monomers having a terminal CH.sub.2 .dbd.C&lt; group, or with polymerizable polyolefinic monomers. For example, when polymerizing vinyl chloride, and other comonomers when used, the same are maintained in the form of discrete droplets in an aqueous suspension system by the use of suspending agents and agitation. When the reaction is complete, the resultant polymer is washed and dried. However, very often these suspension systems are not too stable and during the polymerization reaction, vinyl chloride polymer (PVC) builds up on the inner surfaces of the reactor. Obviously, this polymer buildup must be removed since it results in further formation of polymer buildup which, in turn, results in the formation of a hard crust. This crust formation is difficult and costly to remove.
Various methods have heretofore been proposed to reduce the amount and nature of polymer buildup on polymerization reactor surfaces, such as solvent cleaning, various hydraulic and mechanical reactor cleaners, and the like. While the various methods and apparatus have done an acceptable job, none has proved to be the ultimate in polymer buildup removal. Various coating materials have been proposed for coating the internal surfaces of the reactor which materials are resistant to polymer buildup. For example, in U.S. Pat. No. 4,080,173 there is shown and described the use of self-condensed polyhydric phenols and polyhydric naphthols as coatings to prevent polymer buildup. While these coating materials give good to excellent results, work still continues to find new and better materials with which to coat the internal surfaces of polymerization reactors.